A grue is a term for a fictional predatory monster that dwells in the dark. The word was first used as a fictional predator in Jack Vance's Dying Earth[1] universe (described as being part "ocular bat", part "unusual hoon", and part man).[2]

Dave Lebling introduced a similar monster, whose name was borrowed from Vance's grues, into the interactive fiction computer game Zork, published by Infocom. Zork's grues fear light and devour human adventurers, making it impossible to explore the game's dark areas without a light source.[3] The grue subsequently appeared in other Infocom games.

Due to Zork's prominent position in hacker history and lore, grues have served as models for monsters in many subsequent games, such as roguelike games and MUDs.[citation needed]

A common catchphrase associated with grues is the line that displays whenever players in Zork and related Infocom games enter a dark area without a light source: "It is pitch black. You are likely to be eaten by a grue."

In the fourth Zork game, Beyond Zork, an evil being called an "Ur-grue" is introduced as the primary villain. Though similar in name, the Ur-grue is significantly different from the classic grue, being more akin to an evil god than a simple predatory monster.

Again, Scandinavian and German language may account for this etymology, where the Ur- prefix is used to signify origins (for example, German Ur-ur-grossvater means "great-great-grandfather"). An Ur-grue would be the mother/father of all grues, possibly the first grue, or even Great-grue.

Grues are a common reference in hacker culture or among computer-savvy people.

On IGN's list of the "Top 100 Video Game Villains of All Time", the grue was listed as number 46.[4] When summing up the creature and the development behind it IGN wrote, "The grue's presence may have been a handy solution to a very particular problem in the game design, but it has grown far beyond being a mere gameplay convenience to become one of the chief boogiemen in the early history of video games."

In the popular clicker/idle game Clicker Heroes, a grue may be one of causes of death to your mercenaries. The game tells you that the mercenary was "eaten by a grue".

The video game Don't Starve also has a monster similar in behavior named Charlie. In addition, her name within the game files is also known as "Grue".

The webserialWorm features a supervillain main character, who can produce clouds of amorphous darkness, codenamed Grue.